A valve timing control apparatus controls valve timing of an intake/exhaust valve by changing a rotation phase between a crankshaft and a camshaft of an internal combustion engine. A hydraulic valve timing control apparatus is equipped with a housing rotating with a crankshaft and a vane rotor rotating with a camshaft. The vane rotor defines an advance chamber and a retard chamber in the housing. The vane rotor is advanced or retarded relative to the housing by operation oil supplied to the advance chamber or the retard chamber. The operation oil is supplied by a direction switch valve. The advance chamber and the retard chamber may be referred to oil pressure chamber.
U.S. Pat. No. 7,533,695 B2 describes a direction switch valve for a valve timing control apparatus, and the direction switch valve is a spool-type valve disposed at the central part of the vane rotor. The spool of the direction switch valve has a connection passage which connects an oil pump and an oil pressure chamber according to an axial position of the spool. A check valve is arranged in the connection passage, and is distanced from a discharge hole in the axial direction. The discharge hole is an oil exit of the connection passage.
The check valve includes a cylindrical valve body fixed to the inner wall of the connection passage, a valve seat fixed to the valve body, and a spherical valve object seating on or separating from the valve seat. The check valve restricts operation oil from flowing toward the oil pump from the oil pressure chamber. Thus, when operation oil is supplied to the oil pressure chamber from the oil pump, the operation oil can be restricted from returning from the oil pressure chamber to the oil pump if alternating torque acts on the vane rotor, for example, due to spring reaction force of an intake/exhaust valve.
A clearance is defined between the valve body and the valve object of the check valve, and operation oil flows through the clearance when the valve object is separated from the valve seat. The clearance enlarges the size of the check valve in the radial direction, and enlarges the size of the direction switch valve as a result.
Moreover, the valve-closing part, i.e., the valve seat and the valve object, of the check valve is arranged to distance from the discharge hole in the axial direction, in the connection passage. Therefore, it takes time to close the check valve when operation oil flows backwards from the oil pressure chamber toward the oil pump.